Electromagnetic relay



sept; 3o, 1930.`

`w.`H. PETERSEN MCTROIAGNBTIC RELAY Filed Juno 12. 1929 Jaren EOP.

Nil/zehn Henn i213 fetersn.

am /Lt'orney Patented Sept. 30, 1930 UNITED STATES? PATENT OFFICE WILHELM HENNING PETEESN, E vAsTEEAs, SWEDEN,Y nssIGNoE To ALLMNNA SVENSXA ELEKTBISKA AKTIEBOLAGET,

OF SWEDEN Application mea Jane 12, 1929, serial Nd.

The perpetually increasing demand for safetyv Vin the operation of electric distribution systems lead to corresponding, more and more increasing demands on the relays serving to protect the systems, as regards the sensitivity and reliability of the said relays. The Vsensitivity implies that the relay shall be able to develop strongL forces with a small consumptionof power.V The reliability depends on many factors, among which one of the most i'mportantis that the curve expressing the relation between the displacement of the movable part and the force developed shall have an appropriate course. Another circumstance influencing the reliability is the behaviour of the relay on the occasion of heavy overloads. Particularly in'very sensitive relays which are normally intended to l be actuated by weak currents, a rise of current above a certain value is generally accompanied by accessory phenomena which may hazard the regular function of the relay.

The present invention relates to a relay which is principally intended to operate as a current relay and which is distinguished by a great sensitivity as well as a great reliability. The sensitivity depends mainly on the fact that the armature forms the smallest possible portion of the magnetic circuit. For

this purpose, the stationary portion ofthe magnetic core is interrupted only for a short interval for leaving space for the armature which is movable substantially at right angles to the flux path of the core. The length of the interval should be smaller than, equal to or slightly greater than the length 'of dis- 01E'` VASTERAS, SWEDEN, Al CORPORATION ELEc'rEoMAGNETrc RELAY 376,181, and in sweden october `15, 1923.

attractive force causes risk for heavy vibra-y tions as soon as the relay is operated by alternating current, such vibrations being likely to causeregeated interruptions of current and thereby a urning of the contacts. y A form of the invention is illustrated in the accompanying drawing. Figure l shows the magnetically active portions of the relay in an end view, Figure 2 the entire relay in a side view, and Figure?) a detail of 2 on a larger scale. Figure 1 shows some curves characteristic to the relay.

AReferring to Fig. 1, l'is the mainfportion of the stationary magnet Icore of the relay, which core may be laminated in the usual mannerv and is composed of two legs carrying coils andja lower yoke. shown, the core is also provided with an lupper'yoke 2 which is interrupted only fora short distance so as to leave space for the movablearmature 3. The latter consists preferably of a singlejsheet kiron piecebent in U-shape, the side pieces of which limit the two air gaps of the relay, while the' inter-- mediary bridge piece conducts the flux between the side pieces. As the relay is normally intended toA operatefor very weak cur` rents and thus with weak fluxes in the air gaps, the thin bridge piece of the armature 1s normally suflicient to conduct the entire flux without being saturated. Athigh overcurrents, which always are likely to occur, the restricted flux path through the bridge causes a limitation of the flux in the air gap,

the consequence hereof being that'the armature is'not subjected to forces of t-oo great In the form sif magnitude whichwould give rise to disturb# ances. In order to further enforce this limitation of the HuX, the yoke 2 may also, as shown in the drawing, consist of simple sheet-r ironpieces of which. the ends facing the armature are bent to be substantially parallel to the side pieces of the armature.

In relays in general and particularly in such where a high sensitivity is desired, it is important that the curve expressing the relation between the movement of the arma` ture and the attractive force acting thereony has an appropriate shape. The movement of the armature is generally counteracted by a spring which in Figure` 2 of the drawing is designated by 4. In the same iigure, the armature 3 is shown as mounted on a long lever 5 capable or being swung around a pivot 6 in astand 7 and actuated by the said spring 4. The lcounter-force exerted by the latter generallyincreases in proportion tothe ldisplacement and may in Fig. 4, where the abv the lever 5 on a Vlarger scale, inthe original position in full and in the -ii'nalposition in dotted lines. It is easily seen that an additional count'erlrorce arises at, the Vend. of the movement by reason'of the elasticity of the Contact 9, s'othat the total counter-force durin'gthi's'portion of the movement-can be represented by the straight line b in Figure4. In order 4that the reiay 'shall operate Vin a satisfactory manner it is desirable that theV curve c expressing the relation between magnetic :torce and displacement should follow the broken line a, b as closely as possible and int'er's'ec't'it at no Vvplace after the movementy hasfbegiin, as thisl would cause uncertainty in the function[and'partioularly a bad contact pressure. The curve c should therefore moving sidewise with respect to the flux in said core into said interval, and auxiliary pole pieces limiting an interval adjacent to said first interval and on the side 'or the core towards which the armature is moved whenV attracted. f

4. In electromagnetic relays, a stationary magnet core having an interval, an armaturemoving sidewise with respect to the tina: -in-said core intosald interval, and auxiliary 'WILLM .ernannte P'ETniasnn primarily lrise at 'a comparatively constant Y rate in its major'portion. This can be accompiish'ed by making 4the upwardly directed portions of theyoke 2 and armature 3 oblique so VVas to caus'e'the air gap to decrease as the armature is pulled into the interval in the yo'lie. Further, however, the curve c should be 'considerably steeper towards thewend corresponding to'th'e tinal attraction. In order to' achieve this, a lpairof auxiliary pole pieces 10 are preferably arrangedyinside the ,yoke soas to `causeanincreased attraction on the armature towards 'the endfofits movement. These auxiliarypolepieces also `preferably consist of simple sheet'ir'onwhereby the advantage is gained among others that the last portionbf the 'curve cca'nbe 'adjusted to an appropriate shape lby a 4slight deformation ofthe vsaid pieces.

I claim as my invention l."In electromagnetic relays, a stationary magnet core having bent sheet iron .pieces limiting an 'interval anda U-shaped armature movable into said interval.

2. In electromagnetic relays, a stationary magnet'core having diverging surfaces limiting an interval and a vU-shaped armature having correspondingly divergent side pieces movable into said interval.

3. In electromagnetic relays, a-stationary magnet core having aninterval, an .armature ioni 

